We propose to examine the enzymes of human and animal mononuclear phagocytes from blood, lung, and peritoneum. The enzymes include neutral proteases (elastase and collagenase), lysozyme, angiotensin convertase, cathepsin D, beta-glucuronidase, and enzymes associated with O2 metabolism. Human studies include controls, cigarette smokers, sarcoidosis, asbestosis, and silicosis. We will examine the inhibitor profile, factors affecting enzyme activities and enzyme secretion rates by macrophages with particular emphasis on potential therapeutic agents.